Cervical muscle strength after laminoplasty.

To determine changes in cervical muscle strength after laminoplasty and to evaluate the relation between muscle strength and neck pain, we measured maximum isometric muscle strength using a handheld dynamometer. We also investigated neck pain before surgery and every month after surgery in 21 subjects who had undergone French-door laminoplasty. Muscle strength decreased particularly 1 month after surgery, the extensor muscles being affected more than the flexors. The strength of both muscle groups increased gradually; and at 1 year after surgery they had regained their presurgical status. All of the subjects complained of severe neck pain after 1 month. Their complaints began to decrease a few months after surgery, although they were still present in nine patients at 1 year after surgery. The correlation between muscle strength and neck pain was strongly negative for extension and flexion in men and for extension in women. No correlation was found between flexor muscle strength and neck pain in women. The extension/flexion ratio was significantly high in the neck pain group 1 year after surgery. Our results suggest that symptoms within a few months after surgery are due to surgical trauma to the soft tissues but that chronic neck pain derives from an imbalance of the two muscle strengths.